Eon的海上风电并网导则

Requirements for Offshore Grid Connections in the E.ON Netz Network

E.ON Netz GmbH, Bayreuth

Updated: 1 April 2008

Requirements for Offshore Grid Connections in the E.ON Netz Network

1. Introduction

The following requirements pertain to the grid connections of offshore wind parks in seas, which are referred to here as offshore grid connections.

Except for the deviations and amendments contained herein, the same requirements for the offshore connections basically apply as for all other connections of the Grid for E.ON Netz GmbH (ENE), as defined in "Netzanschlussregeln Hoch- und Höchstspannung" (“Grid Code High and Extra-High Voltage”) (NAR, Updated: 01.04.2006).

The fulfilment of the NAR and of the requirements for the offshore grid connections are an essential condition to ensure a securely operating system, not only for the offshore wind parks, but also for the grid onshore.

2. Legal Framework and Scope

The law which came into effect in December 2006 to accelerate the planning process for infrastructure projects, that is, §17 sec. 2a Energiewirtschaftsgesetz (Energy Industry Act), requires transmission system operators (TSO) to lay out and operate grid connection cables up to the substations for generating plants which are erected in the North and Baltic Seas, and which comply with the Erneuerbare-Energien-Gesetz (Renewable Energy Sources Act). The amended or deviating requirements as set forth herein apply, in combination with the NAR for the grid connection point.

3. Terminology

Generating plant

A generating plant (offshore wind park) can comprise of one or more generation units. It includes all auxiliary operations and units.

Generation unit

A generation unit consists of a single wind energy turbine with the corresponding generator, generator transformer and switching stations in a tower.

Grid connection system

The term grid connection system denotes all connections between the grid coupling point and the connectee. Depending on the connection design, the grid connection system can consist of partial DC transmission (HVDC) or a direct AC connection.

Grid connection point

The grid connection point is the point at which the connectee’s station is connected to the grid connection system. For the offshore wind parks this is the offshore cable sealing end of the grid connection system. Concurrently, it represents the ownership boundary between the connectee’s facility and that of the TSO.

Grid coupling point

The grid coupling point is where the grid connection system of the offshore-wind park is connected to the transmission grid of the ENE onshore.

Abbreviations for the Voltage Levels

HV – high voltage

MV – medium voltage

LV – low voltage (generator voltage)

4. Requirements at the Grid Connection Point

4.1. Voltage and Frequency Characteristics

Supplementary to the NAR section 3.1.7, the following nominal voltage is specified for the grid connection point:

•155 kV: continuous operating voltage of 140 - 170 kV

For individual connections, other nominal voltages are acceptable, subject to ENE approval. The nominal frequency for the offshore grid connection is 50 Hz as in the NAR.

In contrast to the specified frequency range as specified in the NAR section 3.1.7, an extended range is applicable:

•within an uninterrupted continuous operation and within a limited operation of 10 minutes (fig. 3): 47.5 – 51.5 Hz

•limited to up to 10 seconds: 46.5 and 53.5 Hz

4.2. Neutral Point Connection and Layout of the Generating Plant Transformers Supplementary to the NAR section 3.1.8 the following applies:

The grid connection system, including the metallically connected parts, operates at a low resistance neutral point (solidly earthed).

To decouple the zero phase sequence components, improve the symmetry of the line-to-earth- voltage during short circuits, and avoid transmitting odd-numbered harmonics, divisible by three, the HV/MV transformers are to be implemented in the vector group

YN/d5.

Not all of the neutral points at the high voltage side of the HV/MV transformer need a switchable direct connection to earth.

The HV/MV transformers muss be equipped with +/- 6 steps from +/- 13 % by means of a tap changer. This tap changer is to be integrated within the control design of the grid connection. Both the control design and settings are subject to ENE approval.